Investigative clinical therapeutic studies and clinical therapeutic studies in children with acute leukemia, malignant lymphoma, histocytosis X, and malignant solid tumors (brain tumors, neuroblastoma, Wilms' tumor, osteogenic sarcoma, Ewing's sarcoma, soft tissue and miscellaneous malignant neoplasms) are conducted at four levels. 1) Phase I coordinated studies of human pahrmacologic and toxicologic aspects of new anticancer agents and new combination in dosage regimens: 2) Phase II systematic investigations of the effectiveness of individual anticancer agents or treatment program in specific tumors: 3) Phase II comparative evaluations os selected drugs and/or therapy regimes; and 4) Specific laboratory investigations in immunology and laboratory and clinical pharmacology. The functioning cooperative group study mechanism is utilized to increase the size of the study population and to shorten the duration of the study. Members of the project professional personnel participate in the cooperative group study mechanism as study coordinators, intergroup study direction, and scientific program guidance. Independent investigative probes are undertaken to explore leads resulting from or directed towards group studies. Several intergroup and national studies, ongoing and projected (National Wilms' Tumor Study, Intergroup Rhabdmyosarcoma Study, Intergroup Ewing's Sarcoma Study, and Hepatoma Study) are include. Active participation in epidemiological studies is projected. This research will be executed in an integrated multimodel manner. Attention to centralized data management will be given for the individual specialties of pediatrics, surgery, radiotherapy, pathology, and laboratory support. Special attention will be given to current protocols, and protocols to come, employing high dose methotrexate and/or cis-platinum, and protocols requiring classification and pharmacology of lymphoid malignancies, in order to establish proper therapy assignment. The research will be based at M.D. Anderson Hospital as the primary institution and The University of Texas Medical Branch at Galverston as a Satellite.